1. Field of the Invention
The present invention relates generally to the field of pump, and in particular to an improved structure of a pump that comprises a pump body having an opening into which a cap is fit and a rotatable fixing ring is used to secure and thus fix the pump body and the cap together, wherein the cap has an underside from which a projecting ring having a thread extends to engage a thread formed on an end of a piston cylinder to complete assembling so as to achieve the advantages of being easy to assemble and disassemble, reducing components and parts needed, reducing cost, and being applicable to various volumes of the pump.
2. The Related Arts
A variety of pumps are known. FIG. 1 of the attached drawings shows a pumping device that is disclosed in U.S. Pat. No. 7,367,366 own by the present inventor. The pumping device comprises a pump body 10 having a bottom to which a base 11 is mounted to receive a user's foot to step thereon and a top to which a cap 12 is mounted. The pump body 10 receives therein a frame 13 through which a piston cylinder 14 is received to allow an end thereof to connect to and communicate with a first transverse passage. A piston rod 15 extends through the cap 12 into the piston cylinder 14. The piston rod 15 has an end to which a piston disk assembly 151 is mounted. An internal one-way valve is arranged at an end of the first transverse passage located under the piston disk assembly 151 and an external one-way valve 103 is mounted to an opposite end of the first transverse passage. The cap 12 comprises a second transverse passage 121 formed in one side portion thereof and having an end receiving a steel sphere therein, an open end to which a nozzle 123 is mounted, and a middle portion that extends downward to form an upright tube that has an open end to which a manual-operation buoy-based safety valve 125 is mounted. The second transverse passage 121 has a portion that is exposed outside and is formed with an opening for connecting with a first slide valve 126. The first slide valve 126 is connected by an intermediate tube 18 with the external one-way valve 103 for communication therewith. The cap 12 comprises an air inlet valve that comprises an air inlet set 171 forming therein a T-shaped passage comprising an upper horizontal section connected to a control handle 173. The control handle 173 comprises spaced recesses, whereby through the handle being pulled out or pushed in, the spaced recesses may be registered or shifted away to thereby open or close the T-shaped passage of the inlet seat 171. The cap 12 comprises a third transverse passage 16 formed in another portion thereof and having two ends respectively coupled to a second slide valve 161 and a vacuum generator 162 and a further end coupled to a pressurized air control valve 163. The third transverse passage 16 comprises an opening to couple a pneumatic-operation buoy-based safety valve 164. The cap 12 comprises a large fluid opening 165. Through controlling the air inlet valve and the opening condition of the first slide valve 126, manual operation of the piston rod 15 for up and down movement causes vacuum generated inside the barrel to draw in a fluid or causes a rise of internal pressure for expelling the fluid contained in the barrel. Alternatively, pressurized air can be introduced therein and through the opening conditions of the first and second slide valves 126, 161, air contained in the barrel can be evacuated to induce vacuum inside the barrel for drawing in fluid or pressurized air may be introduced into the barrel to causes a rise of internal pressure for expelling fluid from the barrel.
However, such a known pumping device has a complicated structure that requires a large number of parts assembled together to form the pump. The cost is high and the assembling is difficult and time-consuming. Maintenance is also difficult.
For the known pumping device, skilled person is required for maintenance and repairing if components fail or are broken. General users are incapable of disassembling the device for carrying out part replacement. It may also be difficult for the skilled person, who successfully disassembles the device and carries out replacement of parts, to re-assemble the disassembled device. This is because the base and the cap are respectively set at opposite ends of the piston cylinder and to make a perfect positional calibration is in general very difficult. Furthermore, the frame and sealing rings are also necessarily mounted therebetween, where any incorrect positioning would damage the sealing rings or cause undesired leak. In addition, a number of bolts are needed for securing and fixing the components. All these steps of operation must be carried out in a very precise manner, otherwise the device might get destroyed. It is for such a reason that the consumers are encouraged to purchase a new one of the pumping device, instead of repairing of any broken parts for the repairing operation may cause further damage that requires the maintenance operator to pay for.
The known pumping device is of such a structure that the piston cylinder has a fixed length and thus the length of the base and the cap is fixed also for they are fixed to the two ends of the piston cylinder. The pump body is thus invariable in specification. This imposes a constraint on parts stock, unnecessarily increasing stress of parts stock and also increasing the parts inventory, thereby making it adverse for market competition.
Thus, it is desired to provide a solution for overcoming the above problems.